Method for controlling a hydraulic system of a mobile working machine

Abstract

A method is described for controlling a hydraulic system, particularly of mobile working machine, with at least one internal combustion engine driving at least one hydraulic pump with adjustable volumetric displacement and possibly additional fixed-displacement pumps

Description

FIELD OF THE INVENTION [0001] The present invention concerns a method for controlling a hydraulic system, particularly of a mobile working machine, with at least one internal combustion engine driving at least one hydraulic pump with adjustable volumetric displacement and possibly additional fixed-displacement pumps. BACKGROUND OF THE INVENTION [0002] A method for controlling the load limit of a hydrostatic drive and a hydrostatic drive for a machine are described in EP 0 497 293 A1. It detects the position of the accelerator and the actual speed of the internal combustion engine present in the machine by means of metrological instruments and feeds these measured values to an electronic control system. A standard deviation is determined from the difference between the actual and target power levels defined by the measured values and a control valve actuated so that the hydraulic pump accepts hydraulic power lower than or equal to the available power of the internal combustion engine...

AI Technical Summary

Problems solved by technology

The control system can only allow for one load-dependent reduction in the speed of the internal combustion engine which has already taken place.

In addition, the method described only allows for the pump for the hydraulic drive of the self-propelled machine.

Complicated load distributions and changes in them during operation, as commonly occur in complex hydraulic systems with multiple pumps and transmission systems, cannot be controlled satisfactorily by the method described.

However, it is necessary for the speed of the diesel engine to have fallen already so that the mechanical overload can be detected.

In addition, if several adjustable pumps are present, their volume displacement will always be reduced uniformly, rendering flexible adjustment to different operating modes of the plant impossible.

The necessity for a so-called inching pedal constitutes a further disadvantage in modern machines.

However, this complicates the operating procedure for the machine, as the operator has to ensure a diesel engine speed high enough to supply the respective hydraulic systems manually, by operating the inching and accelerator pedals, as well as operating the controls for the working functions.

Images